Computer scientist Professor Manuel Blum has spent his life trying to determine what's on his mind - or at least how it works. Somewhere along the way, he was introduced to computer science by a mentor. Then in 1996, while at the University of California's Berkeley College, he decided to bring his knowledge to Hong Kong as a visiting professor at City University. Set to celebrate his 60th birthday on Sunday, Professor Blum lives on campus at Kowloon Tong with his wife Lenore, who is a maths professor at the university. They have a son and two grandsons. What's on your mind? This conference is going on (the International Conference on Theoretical Computer Science, at City University). I'm very lucky to have the best computer scientists in the world here. If someone planted a bomb here we would lose all these expert computer scientists. What's the aim of the conference? Theoretical computer scientists are interested in ideas and just really love it when someone comes up with a useful new one. These are the kind of ideas that it's possible to make money from. In fact there are many that could be used to make lots of money. The problem is we are so interested in the ideas themselves that we don't make the money ourselves. What kind of ideas? I'll give an example of the idea I'm working on now. When you log on to a computer, you have to tell it your name and password. If someone is looking over your shoulder, he can get it, and if he is listening in on the line, he can get it. I get my students to try and find out what my password is. They don't have much difficulty getting it. Isn't that hacking? Yes, that's hacking. I recommend hacking, it's the best thing for security that we do. If you don't have honest students doing it, then you have dishonest ones instead, and we are stumped. The idea I'm working on is that I would like to be able to sit down and have the computer ask me questions about my password, but questions that don't give any information away. By responding to the questions, I give the computer the password. It's very unlikely the computer will ask people the same questions. I'd like the method to be simple enough for my four-year-old grandson to use. What happens when it's finished? Then I go on to the next idea, and get all my friends upset because I'm making no money from the last one.